This invention relates in general to a fluid displacement device. More particularly, it relates to an improved scroll-type fluid displacement device which has a flow diverter mechanism directing intake fluid flow to break incompressible liquid accumulated in a bearing housing into fine droplets which can be evenly engulfed by two suction pockets formed by the scrolls. This invention also relates to a multiple groove tip seal mechanism for radially sealing off compression pockets formed by the scrolls. This invention further relates to a semi-radial compliant mechanism which maintains radial compliant function of the orbiting scroll and at the same time its orbiting radius is predetermined such that the load on the fixed scroll exerted by the orbiting scroll due to the centrifugal force is shifted to the crank shaft.
Scroll-type fluid displacement devices are well-known in the art. For example, U.S. Pat. No. 801,182 to Creux, discloses a scroll device including two scroll members each having a circular end plate and a spiroidal or involute scroll element. These scroll elements have identical spiral geometry and are interfit at an angular and radial offset to create a plurality of line contacts between their spiral curved surfaces. Thus, the interfit scroll elements seal off and define at least one pair of fluid pockets. By orbiting one scroll element relative to the other, the line contacts are shifted along the spiral curved surfaces, thereby changing the volume of the fluid pockets. This volume increases or decreases depending upon the direction of the scroll elements' relative orbital motion, and thus, the device may be used to compress or expand fluids.
In scroll fluid compression application, it is necessary to supply oil to lubricate shaft bearings and a thrust bearing. Afterwards, the oil accumulates in the lowest spot in the compressor, called an oil sump, as disclosed in U.S. Pat. No. 3,994,633 to Shaffer. The oil is usually then re-circulated by an oil pump. This oil pump, however, not only consumes extra energy, it is also a potential cause of accident when it fails.
U.S. Pat. No. 3,994,636 to McCullough et al. discloses a tip seal mechanism for radial sealing between the compression pockets. In this mechanism, a tip seal is placed in a spiral groove at the tip of the scroll vane. It runs continuously along the spiral groove. The tip seal is urged by either a mechanical device, such as elastic material, or by a pneumatic force to contact the base of the other scroll member, and thus, to provide radial sealing. U.S. Pat. No. 4,437,820 to Tarauchi et al. discloses a mechanism using fluid pressure to drive a tip seal in the tip groove of one scroll member to contact the base of another scroll member. The mechanism disclosed by Tarauchi et al. has three shortcomings:
1) For convenience, the surface of the tip seal going to contact the base of the mating scroll member is called the tip surface. The surface of the tip seal that is opposite to the tip surface is called the back surface. The tip seal in the spiral groove extends from the central area to the peripheral. At different locations, the tip surface of the tip seal is subject to different pressure which can be briefly calculated as the average of the fluid pressure at both of its sides. At the central area, where the pressure acting on the tip surface of the tip seal is high, a high back pressure is needed to push the back surface of the tip seal to overcome the pressure on its tip surface. On the other hand, at the peripheral area, where the pressure acting on the tip surface is low, a low back pressure is needed. A single source of pneumatic force, while enough for the central region, will exert excessive force on the back surface of the tip seal at the peripheral area. This causes excessive friction loss and accelerates the wear of the tip seal. PA0 2) U.S. Pat. No. 4,437,820 requires the tip seal loosely fitted in the groove. Thus, the urging fluid acting on the back surface of the tip seal will leak to the compression pockets from the gaps between the tip seal and the groove. This internal fluid leakage will lower energy efficiency and cause over heating. PA0 3) A long tip seal, running from the central area to the peripheral, is subject to thermal expansion proportional to its length when working temperature increases. The longer the tip seal, the harder it is for it to fit in the groove under different temperatures.
U.S. Pat. No. 4,082,484 to McCullough et al. discloses a fixed-throw crank mechanism with a counterweight mounted on a hub bearing located at the peripheral of the orbiting scroll hub to counteract at least partially the centrifugal force of the orbiting scroll. This mechanism distributes the driving load and the centrifugal load separately onto two bearings, the driving load to the orbiting bearing inside the orbiting hub and the centrifugal load to the hub bearing outside the hub. Thus, the working condition of the bearings is greatly improved. This mechanism is only suitable, however, for a fixed-throw crank and not for a radially compliant mechanism, which has been proven to be a successful arrangement for scroll devices.
U.S. Pat. No. 3,924,977 to McCullough et al. discloses a mechanism having a radially compliant mechanical linking means which also incorporates means (i.e. a mechanical spring) to counteract at least a fraction of the centrifugal force exerted by the orbiting scroll member. This mechanism, however, does not have a counterweight mounted on a hub bearing located at the peripheral of the orbiting scroll hub. When the mass of the orbiting scroll and/or the crank shaft angular velocity become large, the centrifugal force can not be substantially counterbalanced by the linking mechanism. As a result, the flank of the orbiting scroll exerts excessive force caused by the orbiting centrifugal force on the flank of the fixed scroll. Hence, excessive wear and friction between scroll members and fatigue failure of the scroll elements take place.
To overcome the shortcomings of the above mentioned prior art, the present invention eliminates the use of an oil pump by using the suction fluid to carry over accumulated oil and to re-circulate it by the discharge fluid pressure. The present invention provides a flow diverter mechanism that makes intake fluid flowing in a predetermined direction of a channel capable of breaking the accumulated oil into droplets that can be evenly engulfed by two suction pockets formed by the scrolls. The present invention also provides a multiple groove tip seal mechanism for radially sealing off the compression pockets. The present invention further provides a semi-radial compliant mechanism which separately distributes the driving and centrifugal loads to two bearings on the orbiting scroll and maintains the radial compliant function of the orbiting scroll and at the same time transfers the centrifugal force of the orbiting scroll from the fixed scroll to the crank shaft.